There has been extensive work developing lasers using pumped gases to provide high-power laser beams. In particular, pumped gas has been used in diode pumped alkali metal lasers in which a flowing gas is provided in a main cell and a diode laser is used to pump the main cell and create a laser beam propagating down a laser propagation passageway. High-power is achievable in this type of laser in part because the flowing gas provides the right concentration and temperature of both the alkali metal vapor and the hydrocarbon gas in the main cell where the laser beam is created. However, the flowing gas by necessity creates a fairly unstable environment within the laser propagation passageway. Eddy currents, convective effects and the like will cause the gas to flow slightly within the laser propagation passageway, which is undesirable. To prevent the gas from contaminating the window of the laser, the typical solution is to shield the window by providing a continuous flow of gas across the window to prevent the alkali metal vapor from reaching the window. If the alkali metal vapor does contact the window, it will deposit on the window and it will begin to absorb the heat of the laser within the laser propagation passageway. The metal on the window will become very hot and will reach a temperature sufficient to break down the hydrocarbon gas. Then, carbon from the hydrocarbon gas will deposit on the window and reduce the transparency of the window. This phenomenon is called window burning, and it will greatly reduce the power and efficiency of the laser.
The process of using a gas flow to protect the window of the laser can be effective, but it creates mechanical complications and expenses associated with supplying and controlling another gas within the laser and it creates potential problems based on the introduction of yet another gas within laser. The present invention proposes a laser in which alkali metal gases and hydrocarbon gases are flowing through a main cell that does not require flowing a protective gas across the laser window.